For the electricians & electrical engineers out there

[Phil_F_NM]

I have a great love for flashbulbs. I also happen to have a great love for old gear. These things go together well, but flashbulbs are getting harder to find at a decent price these days. Aside from finding a lot at a swap meet or thrift store, they are often sold for about $1 a bulb. That's some big expense there.

So, what I'm proposing is that I take a Leica CEYOO flash unit and transfer the guts from a thyristor flash into the Leica unit.

This takes care of a bunch of issues:
-The aesthetic of the Leica CEYOO flash is much nicer than a modern on-camera strobe.
-The amperage of the flashbulb unit will go down to the mA level so I won't fry my M8. (right now I use either a small pocket wizard or a safe synch for connecting flashbulbs to my M8)
-The flash synch speed will upto 1/250. Right now I have to use <1/30 to allow bulbs time to reach peak intensity.

Any recommendations that aren't snarky? I already have, and use Nikon SB25, 26 and 27 flashes. They are the best, but I'd like something different. And really, I just want to do it to say that I did it.

Phil Forrest

[Brian Sweeney]

I think Phil wants to make the old Leica CEYOO flash into a more modern thyrister controlled electonic flash, not use bulbs. "Look and Feel" of the old flashbulb unit, but more modern electronics and a flashtube. I've not done anything like this, hacking wise. Just about any electronic flash with thyristor circuit made in the last 20 years or so uses low current to fire, does not dump the entire charge through the PC cord/Hot Shoe. A coiled flash-tube, like in the Honeywell Strobonars would conform to the Leica reflector.

Flashtube like this one:
http://cgi.ebay.com/Honeywell-Strobo...item2c565a4487

Coupled with the electronics from a Vivitar 285, the newer variety?

Remember, the older Vivitar 283 dumps the entire capacitor through the camera.

[ErnestoJL]

Phil:
Old flashbulbs were triggered by closing a contact inside the camera´s shutter assy, previous (or simultaneously) to firing the shutter to allow the lamp to deliver it´s full light flow when shutter was triggered.
Voltage used was from 135 to 360 Volts, and this voltage was present at the synch cord all the time.
This is valid too for old electronic flashes as well as those called thyristor units, whose only difference with old units (uncontrolled) was that the flash lamp was switched off by a thyristor based circuit.

During the ´80s, electronics took place of mechanical devices and "dedicated" flash units were made to fit almost every camera brand/model, but those have a significant difference in that the voltage at the synch terminal is very very low, as low as 6 VDC sometimes or even lower.
Usually, the trigger from the camera (talking about the inside) is a transistor acting as a switch but this should be supplied with a very low voltage to avoid destruction of the camera electronics.
I guess this is valid too for the M8 and almost any digital camera of today.
My only advice is to check which kind of flash trigger has the M8 to avoid the need to buy another body (or sending the actual one to repair).
Please take note that many "thyristor" units were made to fit old (mechanical) cameras and this means that most of them have a rather dangerous high voltage at the PC plug.
Hope this helps.
Ernesto

[ErnestoJL]

You´re right as long as the camera works with 5VDC.
A Silicon Controlled Rectifier was the original name gave to what we call today thyristors.
Usually the synch terminal is an open collector limited to perhaps not more than 30 VDC.
Ernesto

[ully]

Ditto PKR.

[Phil_F_NM]

Thanks for all the info!

The M8, M8.2 and M9 are all rated for up to 250v, so I'm no worried about the voltage of a modern flash unit or even that of a Vivitar 283.

Brian's right in that I want the look of the older flash unit with the strobe-ability of a newer flash. My two main reasons are that I can connect a modern strobe directly to my M8 no problem (this eliminates the safe-synch issue but still have to use an adapter) AND that I will save money by not buying more flashbulbs.

I have a CEYOO coming in the mail that I just won for a whopping $.99 on the bay. I won't mind sacrificing that unit to stick a small flash in. I just need to find the donor which will provide the guts and it needs to be small enough that I can still fit batteries enough to power the thing.

The CEYOO flash is about the size of 2 D cell batteries stacked atop one another. It used to take a large 22.5v Carbon-Zinc battery + a capacitor. Now that I can get higher power out of smaller capacitors, the world has miniaturized our camera flashes and we have better batteries with better power characteristics which don't have to pump a ton of amps into magnesium filament to cause them to ignite.

I was thinking of a flash on the order of a little bigger than a Canolite-D. As long as I can figure out the guide number (which the M8 will be perfect for after several exposures) I can have the flash fire at a constant output and just vary my aperture (like all the flashbulb using photographers used to do anyways).

Again, thanks for the suggestions and the info!

Phil Forrest

[Phil_F_NM]

PKR: I'm not planning on getting into the detailed electrical workings of the unit itself, basically I'm just wanting to "change it's clothes." I was remarking about the capacitors in today's flashes vs the giant one that sat atop the battery in the CEYOO when the old Carbon-Zinc batteries were used. It was just a statement about how, with things becoming smaller these days, this job shouldn't be that hard, in theory.

Phil Forrest

[semilog]

Originally Posted by PKR

Most quality flash units use capacitors designed for flash tube use. Others of similar value, may explode working under a speed light environment. Be careful.. even though small, the voltages on speed lights are quite high.

No joke. They call EE's "Sparky" for a reason.

[George Bonanno]

Don't forget the reflector. The size of the reflector on a CEYOO or even a CHICO is meant for a number 5 flashbulb. Now, look at the size of the reflector on a Canolite D or a similar unit. It's small in comparison, isn't it ? And how do you mount the flashtube ? In a plane of X, Y or Z ? Major problems here unless one mounts the flashtube reflector inside the CEYOO's reflector. Now that would be funky indeed.

Always keep in mind the bigger the bulb, the bigger the reflector, the smaller the bulb, the smaller the reflector.

Hey, don't get a shock !

[Arjay]

I'm not sure if I can offer a lot of useful advice, but I found excerpts from a Leica repair book (scroll down to pp 105f) that shows the flash unit disassembled.

Two comments: The new flash bulb must be mounted in such a way that its spark location is (a) precisely on the axis of the unit's tubular casing, and (b) directly in front of the center of the fan-style reflector.

The contents of the casing show that there's not a lot of space to mount the new flash electronics. The innards of my relatively powerful Nikon SB-26 would definitely not fit into the CEYOO casing tube. It would probably be a good idea to mount the flash electronics in a separate case and only have the flash tube in the CEYOO reflector.

[oftheherd]

Interesting thread. Fortunately for me, I have a fairly good supply of flash bulbs still. I do like their light. There was a thread a while back that identified two sellers in Europe who still make and sell flash bulbs. I think not cheap, but not a dollar a bulb. You might try google.

[ErnestoJL]

Originally Posted by PKR

Hi Ernesto;

I pulled my 2nd edition of Horowitz and Hill to look at circuits. They are SCRs in 1998. Could this be a country convention? I know the Shockley Diode (early SCR) was the "naming reference". If I search "SCR + Mouser", Triac and SCR come up. If this is a country thing I would like to know. What do you call a Yig Oscillator? is it the same as in the US?


I just pulled my most recent electronics text "Microelectronic Circuits" Sedra + Smith 2009.. there is no listing in the index for SCR or Thyristor.. nothing. Maybe there is a note in the Spice model library CD .. I didn't look. I feel like a Dinosaur.

Most of the electronics texts available here came from the US, but some others from Europe, so most of the names we use came from the US.
I´m not in microwaves, so I guess a Yig osc. is called the same.

We call thyristors to the unidirectional SCRs, and Triacs to those bidirectional.
Most of the literature came from GE, TI and RCA (do you remember that huge company?), so names are almost the same.
Cheers
Ernesto

[rxmd]

Originally Posted by Phil_F_NM

So, what I'm proposing is that I take a Leica CEYOO flash unit and transfer the guts from a thyristor flash into the Leica unit.

Don't fry yourself. Even if the trigger voltage is low on modern flashes, the tubes are still high-voltage driven.

Opening a flash unit if you don't know what you're doing is a Bad Idea.

[Ron G]

Originally Posted by ErnestoJL

Most of the electronics texts available here came from the US, but some others from Europe, so most of the names we use came from the US.
I´m not in microwaves, so I guess a Yig osc. is called the same.

We call thyristors to the unidirectional SCRs, and Triacs to those bidirectional.
Most of the literature came from GE, TI and RCA (do you remember that huge company?), so names are almost the same.
Cheers
Ernesto

I still have an old RCA tube manual and a solid state devices manual.Ron G

[ErnestoJL]

Originally Posted by Ron G

I still have an old RCA tube manual and a solid state devices manual.Ron G

Glad to know I´m not the only one!
IIRC, mine are SC14 (transistors) and RC20 (receiving tubes), plus some others from Sylvania, Philips and Siemens.
Cheers
Ernesto